Since the invention of liquid crystal
displays in the mid-1960s, display electronics have undergone rapid
transformation. Recently developed organic light-emitting diodes (OLEDs) have
shown several advantages over LCDs, including their light weight, flexibility,
wide viewing angles, improved brightness, high power efficiency, and quick
response.

OLED-based displays are now used in cell
phones, digital cameras, and other portable devices. But developing a
lower-cost method for mass-producing such displays has been complicated by the
difficulties of incorporating thin-film transistors that use amorphous silicon
and polysilicon into the production process.

Now, researchers from Aneeve
Nanotechnologies, a start-up company at the University of California, Los Angeles'
on-campus technology incubator at the California NanoSystems Institute (CNSI),
have used low-cost inkjet printing to fabricate the first circuits composed of
fully printed back-gated and top-gated carbon nanotube–based electronics for
use with OLED displays. The research was published in Nano Letters.

The start-up includes collaborators from the
departments of materials science and electrical engineering at the UCLA Henry
Samueli School of Engineering and Applied Science and the department of
electrical engineering at the University
of Southern California.

In this innovative study, the team made
carbon nanotube thin-film transistors with high mobility and a high on–off
ratio, completely based on inkjet printing. They demonstrated the first fully
printed single-pixel OLED control circuits, and their fully printed thin-film
circuits showed significant performance advantages over traditional
organic-based printed electronics.

"This is the first practical
demonstration of carbon nanotube–based printed circuits for display backplane
applications," says Kos Galatsis, an associate adjunct professor of
materials science at UCLA Engineering and a co-founder of Aneeve. "We have
demonstrated carbon nanotubes' viable candidacy as a competing technology
alongside amorphous silicon and metal-oxide semiconductor solution as a
low-cost and scalable backplane option."

This distinct process utilizes an inkjet
printing method that eliminates the need for expensive vacuum equipment and
lends itself to scalable manufacturing and roll-to-roll printing. The team
solved many material integration problems, developed new cleaning processes and
created new methods for negotiating nano-based ink solutions.

For active-matrix OLED applications, the
printed carbon nanotube transistors will be fully integrated with OLED arrays,
the researchers say. The encapsulation technology developed for OLEDs will also
keep the carbon nanotube transistors well protected, as the organics in OLEDs
are very sensitive to oxygen and moisture.

The technology incubator at the CNSI was
established two years ago to nurture early-stage research and to help speed the
commercial translation of technologies developed at UCLA. Aneeve
Nanotechnologies LLC has been conducting proof-of-concept work at the tech
incubator with the mission of developing superior, low-cost, high-performance
electronics using nanotechnology solutions that bridge the gap between emerging
and traditional platforms.